Hydrogen elimination and thermal energy generation in water-activated chemical heaters

ABSTRACT

Less hazardous methods for generating thermal energy for heating water, medical supplies or comestible products using improved flameless chemical heaters/flameless ration heaters by novel chemical or electrochemical means, each capable of suppressing the generation of hydrogen gas. Remote unit self-heating meals may be more rapidly heated by forming a reaction mixture comprising magnesium or a magnesium-containing alloy, and a hydrogen eliminator or suppressor, and introducing water to react the reaction mixture and generate a more rapid release of thermal energy sufficient to effectuate a more accelerated temperature rise and more rapid heating of medical supplies, water, rations or other comestible substances while simultaneously suppressing or eliminating the generation of potentially hazardous hydrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of application Ser. No.12/069,995, filed on Feb. 14, 2008, which is a Continuation-in-Part ofapplication Ser. No. 11/657,852, filed Jan. 25, 2007, which claims thebenefit of Provisional Application Ser. No. 60/764,213, filed on Feb. 1,2006, which applications are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract Nos.W911QY-06-C-0021, W911QY-07-P-0335 and W911QY-08-C-0096 awarded by theDepartment of Defense. The government has certain rights in theinvention.

BACKGROUND OF THE INVENTION

Flameless Chemical Heaters (FCH), also known as Flameless Ration Heaters(FRH), are used in Meal, Ready-to-Eat (MRE) packaging to provide hotmeals to soldiers in the field or for warming or heating medicalsupplies or food rations in confined spaces (e.g., tents, underwatershelters) or in remote locations where there is no heat source. TheseFCHs or FRHs are generally based on the reaction of magnesium with waterto form magnesium hydroxide and hydrogen which releases about 85 kcal ofenergy per mole of magnesium.

There are two types of MREs. The first is an individual meal for thesoldier. The second one is a family-style meal for a group of 10-20soldiers, called the Unitized Group Ration-Express (UGR-E). Both ofthese MREs use a Flameless Ration Heater (FRH) as the heat source forthe hot meal. The temperature of a 250 gram individual MRE entrée can beraised by 100° F. in about 10 minutes using a 14 g FRH. Typically, theprocess of heating food consists of adding about 40 ml of water to theFRH by the military or other user, in order to activate the chemicalreaction that produces the heat. Presently, the FRH consists of amagnesium, iron and salt mixture. The iron is used to activate thereaction of magnesium with water, whereas the salt prevents theformation of a magnesium oxide film on the magnesium metal surface. Thereaction products are magnesium hydroxide and hydrogen. With theindividual MRE, the liberation of up to 13 liters of hydrogen gas hasnot been a substantial safety problem.

The Unitized Group Ration-Express (UGR-E) is a complete meal in a boxand can feed small groups of eighteen soldiers. Again, the food isheated by using a proportionally larger FRH that is activated by theaddition or distribution of water. The problem associated with therelease of hydrogen is significantly magnified with group meals. For aUGR-E weighing 28 pounds and requiring approximately 400 g of heatermaterial, the amount of hydrogen released is typically 13.5 cubic feetor 380 liters. Thus, the concern is that generation of this largequantity of hydrogen in a confined space will exceed the Lower ExplosiveLimit of 4%.

Accordingly, there is a need for an improved system for the elimination,or at least minimization of hydrogen generation in magnesium/water basedflameless heaters.

SUMMARY OF THE INVENTION

It is therefore a principal object of the invention to eliminate orsuppress the cogeneration of hydrogen in all types of magnesium-basedFCHs, to prevent the release of hydrogen into the atmosphere andpreventing potentially explosive situations by means of a novel process.

Thus, one principal aspect of the invention includes useful methods forgenerating energy for flameless heating, such as for foodstuffs, water,medical supplies, etc., especially in the case of outdoor applicationsfor camping, emergency, military applications all without thecogeneration of hazardous hydrogen by the steps of:

(i) forming a reaction mixture comprising at least magnesium or amagnesium-containing alloy and a hydrogen eliminator or suppressor, and

(ii) reacting the reaction mixture of (i) by introducing water togenerate sufficient energy for heating an adjacently package substanceor article, such as water, medical supplies, comestible substances,etc., while simultaneously eliminating or suppressing the cogenerationof potentially hazardous hydrogen.

This inventor discovered a new class of useful hydrogen suppressors oreliminators for flameless heaters.

Accordingly, it is still a further principal object of the invention toprovide novel methods and compositions of matter for the flamelessgeneration of thermal energy, including heater devices and meal,ready-to-eat packaged meals wherein the methods and compositions notonly suppress or eliminate the cogeneration of potentially hazardoushydrogen, but surprisingly, were discovered to provide a substantiallyaccelerated temperature rise for more prompt heating of the packagedmeal compared to other state-of-the-art flameless chemical heaters.

Generally, for purposes of this invention the expression “hydrogensuppressor” as appearing in the specification and claims is intended tomean any metal-containing oxidizing agent that is suitable for at leastminimizing, and more preferably, eliminating the cogeneration ofhydrogen in the presence of magnesium or a magnesium-containing alloy.The metal of the metal-containing oxidizing agent, more specifically, isone having multiple valences, and includes as a preferred group, oxidesof transition metals, such as manganese and/or oxides of ruthenium, andmore particularly, manganese dioxide and ruthenium dioxide, to name buta few.

It should be understood, there are other representative examples ofreactants in addition to oxides of manganese and ruthenium as hydrogensuppressors or eliminators, which when mixed with magnesium and reactedwith water at least minimize, and more preferably totally suppress thecogeneration of hydrogen, while effectively generating the desiredthermal energy. Generally, the useful hydrogen suppressors oreliminators are transition metal oxides that avoid the cogeneration ofhydrogen in the reaction with magnesium or magnesium alloys.Representative examples include noble metals, such as platinum, iridiumand rhodium. Other multivalent transition metal oxides include suchmembers as iron, cobalt, nickel, silver, gold, tin, zirconium, hafnium,tantalum, lead, copper, and so on.

Useful magnesium-containing alloys for the above reaction mixture canalso include at least one alloying element, such as iron, cobalt,nickel, zinc, aluminum and mixtures thereof.

The subject invention also contemplates optional additives in practicingthe flameless heating methods disclosed herein comprising at least onemember selected from hydrogen overvoltage suppressors, promoters,flowing agents and reaction activators.

As previously mentioned, it is still a further principal object of theinvention to provide novel hydrogen suppressing or eliminatingflameless, thermal energy generating chemical compositions. Thecompositions comprise reaction mixtures having at least: magnesiumand/or a magnesium-containing alloy, a hydrogen suppressor or eliminatorthat when mixed with water will initiate the flameless heat generatingreaction.

Generally, the reactants are present in proportional amounts sufficientto generate heat for promptly raising the temperature of substances,products or articles, such as water, medical supplies, consumablerations, and the like, to the desired temperature within a reasonabletime period. As previously pointed out, it was surprisingly andunexpectedly discovered the novel hydrogen suppressor or eliminatorcompositions of the present invention provide a substantiallyaccelerated temperature rise over known flameless heat generatingcompositions comprising magnesium and water.

As previously mentioned, the hydrogen suppressing or eliminatingflameless heat generating compositions may have other optionalreactants, such as a hydrogen overvoltage suppressors, reactionpromoters, flowing agents and reaction activators.

In addition to magnesium metal, the hydrogen suppressing, flameless heatgenerating reaction mixtures may also be prepared from alloys ofmagnesium, prepared from alloying metals, such as iron, cobalt, nickel,zinc, aluminum and mixtures of the same. Such alloys are known amongskilled artisans, and are commercially available through ordinarychannels of commerce.

Besides magnesium, the flameless heat generating reaction mixtures, likethe previously described methods, also comprise at least one hydrogeneliminator/suppressor, such as oxides of manganese and/or ruthenium, andmore particularly, manganese dioxide and/or ruthenium dioxide in asufficient amount to suppress the generation of hydrogen. This includesother transition metal oxides like those previously discussed inconnection with the methods of the invention.

It is yet a further principal object of the invention to provide forheater devices, such as trays and pouches comprising the hydrogensuppressing, flameless, heat generating compositions, particularly forheating water, food rations, including medical supplies especiallyuseful for camping and military applications. This is especiallyintended to include Meal, Ready-to-Eat military ration packagingcomprising the above flameless heater devices.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the invention and its characterizingfeatures reference should now be made to the accompanying drawingswherein:

FIG. 1 is a top plan view of a porous sealed packet of flameless heatgenerating composition of the invention with a portion of the poroussealed cloth removed to show the milled composition;

FIG. 2 is a partial isometric view of a flameless heater containmentpouch of the invention with a portion of the front panel removed for aninterior view of the pouch with the porous packet of heat generatingpowder and the food ration packet;

FIG. 3 is similar to that of FIG. 2, except the containment pouch hasbeen placed in a containment box, and water is being introduced into theflameless heater containment pouch for initiating the generation of heatfor heating the food packet in the pouch;

FIG. 4 is a side elevational view of the containment box with a sidewallof the box removed to show the arrangement of the flameless heater pouchwith sealed food ration packet in the pouch like that of FIG. 3, andwith water added, wherein the box is propped up at the open end toassure the water remains in contact with the porous packet of heatgenerating powder;

FIG. 5 is a plot illustrating the rate of temperature rise of theflameless heat generating composition of the invention relative to therate of temperature rise of prior art composition;

FIG. 6 is a further plot of the rate of temperature rise of anotherembodiment of the flameless heat generating composition of the inventionrelative to the rate of temperature rise of a prior art composition;

FIG. 7 is a further plot of the rate of temperature rise of additionalembodiments of the flameless heat generating composition of theinvention relative to the rate of temperature rise of a prior artcomposition; and,

FIG. 8 is a further plot of the rate of temperature rise of yet anotherembodiment of the flameless heat generating composition of the inventionrelative to the rate of temperature rise of a prior art composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to novel methods and reactionmixtures/compositions for the generation of flameless heat mainlywithout the co-generation of potentially hazardous hydrogen previouslyassociated with prior art methods and compositions. The methods of theinvention employ at least one transition metal oxide powder, such as anoxide of manganese and/or ruthenium, for example, mixed with powderedmagnesium or magnesium-containing alloy to generate flameless heat, freeof, or with minimal cogeneration of hydrogen. The methods of theinvention can be demonstrated by the following representative reactionscheme:Mg^(o)+2MnO₂+H₂O→Mn₂O₃+Mg(OH)₂+Δ

The reaction eliminates or suppresses hydrogen generation, or at leastminimizes its cogeneration, while providing accelerated temperature riseover prior methods, i.e., more spontaneous heat generation than theknown Mg+H₂O reaction, as will be demonstrated by the methods belowcurrently used in flameless chemical heaters or flameless rationheaters. It may be noted that the addition of CuCl₂, NaNO₃, andtrichloroacetic acid to magnesium were believed to eliminate thehydrogen evolution reaction. However, NaNO₃ and trichloroacetic acid arenot effective in fully suppressing hydrogen generation, and CuCl₂ in theMREs is not acceptable because of environmental and healthconsiderations.

The novel chemical compositions of the present invention react andgenerate sufficient heat for promptly heating water, medical supplies,consumable rations, and the like, without simultaneously generatinghydrogen. Methods of the invention rely on a metallic element, e.g.,magnesium or alloy thereof, a hydrogen suppressor or eliminator, andwater, the latter of which acts as a reactant and a medium for thereaction. Generally, the hydrogen suppressor or eliminator is atransition metal oxide, and include inter-alia noble and non-noble metaloxides. Other useful representative oxides include PtO, IrO₂, RhO₂,Fe₂O₃, Co₃O₄, NiO, Ag₂O, Au₂O₃, CuO, TiO₂, ZrO₂, HfO₂, Ta₂O₅ and PbO₂.

Optional additives for the hydrogen suppressing flameless heatgenerating chemical compositions and methods may include a hydrogenovervoltage suppressor, a promoter, flowing agent, activators, and thelike.

The metallic element in the chemical composition that generates heat ismagnesium or magnesium alloy containing from about 0.001% to about 10%iron, cobalt, nickel, zinc, aluminum, either singly or in combinationwith each other. A preferred composition is pure or substantially puremagnesium with small or trace amounts of other metals, e.g., <0.001% toabout 0.1% of the alloying elements, iron, cobalt, nickel, zinc andaluminum. One preferred hydrogen suppressor in the chemical compositionis MnO₂ and RuO₂. A preferred hydrogen suppressor may be either γ-MnO₂or β-MnO₂, both known oxides, made either electrolytically or chemicallyby known methods, or from a naturally occurring ore that is treated. Theamount of MnO₂ in the chemical composition is in ranges from about 1 toabout 10 times the stoichiometric amount required for the Mg+MnO₂reaction with water, the preferred amount being 1-10 times thestoichiometry.

The hydrogen overvoltage suppressor in the chemical composition may be ametal sulfide, the metal preferably being Fe, Co, Ni, or a highlyelectrically conductive carbon, present in amounts ranging from about0.001 to about 1%. The promoter in the chemical composition ispreferably a carbon in particulate or powder form, present in an amountranging from about 0.001 to about 20 percent-by-weight. The filler orflowing agent includes such representative members as silicon dioxideand calcium carbonate, and is present in an amount ranging from about0.001 to about 10 percent-by-weight. They are effective in alsopromoting the reaction rate of the flameless heater reaction mixtures.Activators for the reaction mixtures include alkali metal halides, suchas NaCl, magnesium halide salts, such as MgCl₂, MgBr₂, includingMg(ClO₄)₂, and so on. Additionally, activators for the reaction mixturesinclude thermally and electrically conducting, high surface areasynthetic graphite and other conducting carbon materials. An example ofa suitable synthetic graphite includes Asbury 4827, produced by AsburyGraphite Mills, Inc., of Asbury, N.J., while suitable conducting carbonsinclude Asbury TC 307, also produced by Asbury Graphite Mills, Inc.,KETJENBLACK® (such as EC600JD), produced by Akzo Nobel Polymer ChemicalsLLC, of Chicago, Ill., BLACK PEARLS® 2000 or 1300, both produced byCabot Corporation, Alpharetta, Ga. The amount of activator can vary inthe range from about 0.001 to about 50%. One preferred activator isMgCl₂, the other being electrically conductive carbon.

The reaction scheme set forth supra is an electrochemical corrosionreaction, the anodic reaction being the oxidation of Mg to form Mg²⁺ions, the cathodic reaction being the reduction of MnO₂ to Mn₂O₃ and theelectron transfer processes proceeding on the surface of MnO₂. It is forthis reason that there is no need for a conducting electrolyte, such asa salt solution, to activate the reaction described supra. However, Mgis prone to form MgO and therefore, the reaction described supra doesnot proceed to completion unless an electrically conducting materialsuch as carbon is added to the Mg/MnO₂ mixture and blended thoroughly toestablish/provide good electrical connectivity between MnO₂ and Mgsites.

MgCl₂ serves the same purpose but in a different way. Thermodynamicpotential-pH diagrams for an Mg/water system at various temperaturesshow that the pH at which Mg²⁺ is in equilibrium with Mg(OH)₂ shifts tolower pH values as the temperature increases. Thus, when MgCl₂ is added,the temperature rises to as high as 120-150° C., and facilitates thesolubility of Mg(OH)₂ at pH=7, which is the pH of the water added to thereactants. Note that at pH=7 and at 25° C., the stable species is Mg²⁺,whereas at pH=7 and at 90° C., there is an equilibrium between these twospecies. This is the reason why addition of MgCl₂ promotes theaccessibility of the blocked MgO sites. The pH value at which Mg²⁺ is inequilibrium with Mg(OH)₂ is strongly dependent on the activity of Mg²⁺ions in the solution. It has been found that the higher the activity,the lower the pH value. We generally added MgCl₂ corresponding to anactivity of >>1.

It will be understood, activators, e.g., MgCl₂ and carbon, may beintroduced into the flameless heater compositions of the invention byvarious methods. For example, one method provides for blending/mixing anactivator, such as MgCl₂ or and/or carbon in particulate form into themilled magnesium and hydrogen suppressor or eliminator when preparingthe reaction mixture, before introducing the water reactant.Alternatively, an aqueous solution of the MgCl₂, e.g., 5 to 7 M solutionof the activator in the water reactant (45 to 60 wt % solution), can beprepared and introduced together as a salt solution into the milled Mgand hydrogen suppressor or eliminator reaction mixture. However, theformer method of blending the activator with the milled Mg and hydrogensuppressor or eliminator is generally more preferred because it is moreeffective in suppressing hydrogen than the latter method.

EXAMPLE 1

In order to demonstrate the details of the invention based on aMg/MnO₂+H₂O system according to the equation [1] below, the followingexperiment was conducted:Mg+2MnO₂+H₂O→Mg(OH)₂+Mn₂O₃  [1]

A 99.98% pure Mg metal sample of 500% particle size from Superior MetalPowders, Franklin, Pa., was used in this test, and contained traceamounts, i.e., 85 ppm Al, 4 ppm Cu, 300 ppm Fe, 250 ppm Mn, 50 ppm Na,150 ppm Si, 100 ppm Zn and 50 ppm Ca. In addition, a 300% size γ-MnO₂powder from Tronox, LLC, Henderson, Nev., was used with a purity of 99%.The γ-MnO₂ contained trace amounts, i.e., 8600 ppm S, 2600 ppm Ca, <100ppm Mg, <1000 ppm Al, <100 ppm Si, <100 ppm Cl, 700 ppm K, <1000 ppm Crand <100 Sn ppm.

The above Mg and γ-MnO₂ powders were used to make a batch sample in astoichiometric ratio according to equation [1], above. Approximately 500g of the 300% particle size MnO₂ and 69.44 g of 500μ Mg were combinedand placed in a mill. In this case the mill was a Vibrokinetic Energy(VKE) Mill, from Microgrinding System, Inc., Little Rock, Ark., model624 (diameter=6″ and tube length=24″). This mill was operated with 36stainless steel rods (6 with a diameter=1″, 30 with a diameter= 7/16″)with a length of 24″. The sample mixture was introduced into the millvia a 2″ diameter feed. All the screws and openings were tightened andsecured prior to running the mill for 6 hours. At the end of the 6 hourmilling period, the sample remained in the mill over night to cool. Thesample was removed with a Nalgene scoop, transferred to a 600 mlstainless steel beaker and stored in a desiccator with calcium sulfateas the dehydrating agent.

Following FIG. 1 of the drawings, polypropylene bag 10 was fabricatedfrom porous filter cloth 12 (Unilayer 270), available from MidwestFiltration Company, Cincinnati, Ohio. The filter cloth was a 6-ply sonicbonded polypropylene laminate having a thickness of 22 mils (0.5588 mm),a weight of 91.6 g/m², an air permeability of polypropylene 635 l/m²/secand a Mullen Burst strength of 80 psi. The porous filter clothfabricated from polymeric fibers allows the transmission of water, andthe release of gases while precluding the blockage of pores by the solidreactants and/or products owing to its depth loading characteristics. An8″×11″ sheet of the filter cloth was used to fabricate bag 10 forcontainment of milled Mg/MnO₂ reaction mixture 20 supra. It should beappreciated that as described infra bag 10 may be constructed in avariety of ways. For example, filter cloth 12 may be constructed from asingle layer of 6-ply sonic bonded polypropylene laminate as shown inFIG. 1, or filter cloth 12 may be a dual layer bag consisting of twodifferent filter cloth materials such as polyester fibers for one layerand polypropylene fibers for another layer, and either layer may be theinner or the outer layer of bag 10. Additionally, filter cloth 12 may beconstructed from multiple layers of polyester fibers, e.g., four to sixlayers, or may be constructed as a dual composite fabric consisting ofan inner layer of spunbond/meltblown/spunbond filter media containing100% polypropylene and an outer layer of a 3-ply bonded polypropylenefiber cloth. An example of such an inner layer is Unipro 260-SMS whichis made of white spunbond/meltblown/spunbond filter media containing100% polypropylene with a thickness of 19 mils (0.4826 mm) and a weightof 2.60 oz/yd² (91.96 g/m²), with an air permeability of 17.1 cfm/ft²(86.9 l/m²/sec) and a Mullen Burst of 71 psi. It should further beappreciated that the foregoing examples are within the spirit and scopeof the claimed invention.

First, filter cloth 12 was cut into a 6″×8″ sheet. The filter cloth wasthen made hydrophilic. One of two procedures and surfactants may be usedin making the porous filter cloth hydrophilic. One method employs a “dipand nip” technique. This method requires taking the porous hydrophobiccloth and dipping it into a 5% aqueous solution of surfactant. Theexcess surfactant is then squeezed off by passing the cloth through apair of nip rollers. The second method provides for applying a dab ofPluronic-25R2 surfactant, from BASF Corp., Florham Park, N.J., on one orboth sides of the cloth.

Hydrophilic porous filter cloth 12 was then fabricated into bag 10 byfolding the treated 6″×8″ sheet in half. The bottom 4″ of side 14 and 6″of side 16 were heat sealed to form the pocket or bag 10 with opening 22on the top 4″ of side 18 left open to allow for filling before applyingthe final heat seal. The heat seals were made using a Uline 8″ impulseSealer (H-163). 100 g of the milled and dried Mg/MnO₂ powder 20described supra was then placed in the Unilayer 270 polypropylene bag 10and opening 22 on the top sealed closed. This sealed flameless rationheater reaction mixture bag 10 was then placed in green non-porous“poly” bag 24 (FIG. 2) having bottom closure seal 26 and upper opening28. Poly bag 24, fabricated with a polypropylene film, had a capacitysufficient for also holding 250 g of water as “water test pouch” 30 usedas a surrogate for a regular food ration packet. Poly bag 24 containingthe reaction mixture bag 10 and water test pouch 30 were placed in“chipboard box” 34 (FIG. 3).

60 ml of water 31 (FIG. 3) were then added to green poly bag 24 on thesame side as the ration heater and the top of bag 24 was folded over(not shown). The green poly bag, and its contents in “chipboard box” 34(FIG. 4) were held substantially horizontally with the rationheater/reaction mixture bag 10 below water test pouch 30. After 30seconds, the system was set at a slight incline (FIG. 4), to preventwater loss, and allowed to react for 30 minutes. The temperaturevariation was recorded as a function of time and shown in FIG. 5, andtagged “Present Invention Example 1”.

Example 2

In order to compare the performance of the hydrogen suppressing,flameless heat generating composition of the invention preparedaccording to Example 1, a second sample of the known flameless heatgenerating composition comprising Mg and H₂O only was prepared.

8 g of 500μ Mg/Fe, from Innotech Products, Inc., Cincinnati, Ohio aspresently used in a U.S. Army ration heater, was prepared according tothe recipe in U.S. Pat. No. 5,611,329. This sample was placed in a“non-woven” bag material from Innotech Product, Inc. The Innotech bagmaterial was a roll configured into four, 1″ compartments distributedthrough the length of the roll. 6″ of this material was cut from theroll and the bottom was heat sealed with a Uline, 8″ impulse sealer(H-163). Each of the four compartments was filled with 2 g of the Mg/Feand the ration heater was heat sealed closed (not shown).

The completed flameless ration heater was placed in a green polyethylenebag, from the U.S. Army, with a 250 g water pouch. After thirty seconds,40 ml of an aqueous solution of 0.25 M sodium chloride was pouredbetween the water pouch and the flameless ration heater. The top of thegreen bag was folded over and the green bag with its contents was placedin a “chipboard” box (not shown). For approximately 30 seconds, the boxsystem was held horizontally with the ration heater at the bottom. Then,the system was set at a slight incline to prevent water loss, andallowed to react for 30 minutes. The temperature variation was recordedas a function of time and shown in FIG. 5, tagged as “Prior Art Example2”.

FIG. 5, which plots test pouch temperature relative to time (minutes),demonstrates a significantly faster and higher (steeper) heat elevationtemperature occurring with the flameless heating Mg/Mn oxide reactionmixture prepared according to Example 1 of the present inventionrelative to the known flameless heater composition of the prior artemploying Mg/Fe reaction mixture without transition metal oxide (Example2).

Example 2A

100 g of 500μ Mg/Fe, from Innotech Products, Inc., Cincinnati, Ohio aspresently used in a U.S. Army ration heater, was prepared according tothe recipe in U.S. Pat. No. 5,611,329. This sample was placed in an8″×11″ bag made from the “non-woven” bag material from Innotech Product,Inc., that was configured into four, 2″ compartments distributed throughthe length of the roll. Each of the four compartments was filled with 25g of 500% Mg/Fe and the ration heater was heat sealed closed.

This completed ration heater was placed in a UGR-E heating tray, overwhich a 3500 g “water pouch” was placed. This assembly was placed in acard board box and then 330 ml of 1.5% NaCl solution was added. The cardboard box was then closed and the edges sealed with a tape. Thetemperature variation was recorded as a function of time over a 60 mperiod, and shown in FIGS. 7 and 8, tagged as “Prior Art Example 3”.

Example 3

In order to demonstrate a further embodiment of the subject inventionwhich includes a metal halide activator, a further experiment wasperformed with the reactants: Mg+MnO₂+MgCl₂ by means of the followingprotocol.

The milling procedure for the Mg/MnO₂ mixture was the same as thatstated in Example 1. 45 g of the milled Mg/MnO₂ mixture was mixed with15 g of 325 mesh MgCl₂, from Sigma-Aldrich, Inc., St. Louis, Mo. ThisMg/MnO₂/MgCl₂ mixture was placed in a dual layer bag consisting of twodifferent filter cloth materials made of polyester fibers (Finon C305NW)and polypropylene fibers (Unilayer 270). Finon C305NW is made ofpolyester fibers with a thickness of 7 mils (0.1778 mm) and a weight of50.9 g/m², with an air permeability of 1,778 l/m²/sec and a Mullen Burstof 50 psi. This dual layer configuration is essential with Mg/MnO₂/MgCl₂mixtures to provide thermal stability to the bag via the polyesterfabric and the depth loading characteristic via the polypropylene,6-ply, Unilayer. Both of the bag materials from Midwest Filtration werereceived in 8″×11″ sheets and cut into 6″×8″ sheets. To make thesematerials hydrophilic, the “dip and nip” process of Example 1 wasemployed. To configure the pouch, the Finon polyester material wasplaced aside the smooth surface of the Unilayer polypropylene and bothare folded in half to make a 4″×6″ pouch with the polyester inside theUnilayer polypropylene (not shown). A Uline 8″ impulse Sealer (H-163)was used to heat seal the two materials together. The 6″ side, parallelto the fold and one of the 4″ sides were sealed prior to adding thereaction mixture. An additional seal, parallel to the 6″ side and downthe center of the pouch was also added to make the pouch into twocompartments. 30 g of the Mg/MnO₂/MgCl₂ mixture was added to each of thecompartments. The pouch was heat sealed closed and placed in a green“polybag” with a 250 g water test pouch as a surrogate for a ration. 40ml of water was added to the green bag on the same side as the rationheater. The top of the bag was folded over and the whole system wasplaced in a “chipboard” box. For approximately 30 sec, the box was heldhorizontally with the ration heater under the water pouch. Then thepouch was set at a slight incline for thirty minutes, as in Example 1.The temperature variation was recorded as a function of time and shownin FIG. 6, and tagged “Present Invention Example 3.”

The performance of the FRH composition of the “Present Invention Example3” was also tested relative to the “Prior Art Example 2” with theresults demonstrated by FIG. 6 of the drawings.

FIG. 6 illustrating the performance of the FRH composition of thepresent invention (Example 3) comprising Mg and MnO₂, plus MgCl₂activator also provided a significantly faster and higher (steeper) risein the generation of thermal energy relative to the known flamelessheater composition of the prior art employing Mg/Fe reaction mixturewithout transition metal oxide (Example 2).

Bag Materials

As described above, bag 10 may be constructed in a variety of ways. Asset forth in Example 1, bag 10 may be fabricated from porous filtercloth, such as Unilayer 270. In this example, the filter cloth is a6-ply sonic bonded polypropylene laminate. Additionally, as set forth inExample 3, a dual layer bag consisting of two different filter clothmaterials may be fabricated from polyester fibers, such as Finon C305NW,and polypropylene fibers, such as Unilayer 270. Furthermore, it has beenfound that bag 10 may also be fabricated from multiple layers, e.g.,four to six layers, of polyester fibers, such as Finon C305NW. Similarto the previously described fabrications, the multiple layers can besonically bonded and made hydrophilic by the “dip and nip” process ofExample 1. Each of these fabrications provides varying levels of thermalstability and depth loading capability so that fine particles areprevented from blocking the pores and preventing entry of water fromoutside to the reactants inside the bag material. In the dual layerconfiguration, the polyester fiber provides thermal stability to the bagwhile the polypropylene provides the depth loading characteristic.Moreover, porous filter cloth fabricated from polymeric fibers allowsthe transmission of water, and the release of gases while precluding theblockage of pores by the solid reactants and/or products owing to itsdepth loading characteristics.

It has been found that with when Unilayer-based ration heater pouchesare used in combination with the present invention, a very small seepageof carbon and/or MnO₂ fines occurs before and after the reaction. Suchleakage leads to an unappealing aesthetic appearance of the heater andstains the hands of the person handling the heater. It has been foundthat these issues may be eliminated by employing a dual composite fabricconsisting of an inner layer of 1.5 oz, Unipro 260-SMS(spunbond/meltblown/spunbond filter media containing 100%polypropylene), and an outer layer of Unilayer 135 which is a 3-plybonded polypropylene fiber cloth. The temperature-time profiles of thepresent invention in combination with the Unilayer 270 and the Unilayer135/Unipro-SMS arrangements described above are shown in FIG. 7 andlabeled “Unilayer 270” and “Unilayer 135+Unipro-SMS”, respectively. Theforegoing examples depicted in FIG. 7 are shown with an UGR-E heater,and the test procedure is set forth in Example 20 below. A prior artexample is also shown in FIG. 7 and labeled “Prior Art Example 3”. Ithas been found that use of the above described Unilayer 135/Unipro260-SMS fabric not only improved the heating rate, but also effectivelyprecluded leakage of carbon and/or MnO₂ fines.

Hydrogen Generation

The amount of hydrogen generated by the FRH reaction mixtures of thepresent invention (Examples 1, 3 and 20) was measured on a comparativebasis with the FRH reaction mixture of the prior art (Example 2) bycollecting off-gases and analyzing for hydrogen content by means of gaschromatography. The results are provided in Table 1 below:

TABLE 1 Example Solid Reactants Liquid Reactants Hydrogen Suppression  1Mg/MnO₂ Water 99%  2* Mg/Fe Water + NaCl** 0%  3 Mg/MnO₂/MgCl₂ Water 94%20 Mg/MnO₂/C Water 97.1% 99.7% 20*** Mg/MnO₂/C Water + NaCl 98.9%*Results same as Mg/Fe/NaCl (0.6 g) + Water **Water containing 40 gH₂O + 0.6 g NaCl ***Same composition as Example 20, however liquidreactant is water having 1.5% NaCl

Example 4

The following example demonstrates the method for removing residualmoisture (3.3% H₂O) from electrolytic manganese dioxide to near zerolevel for improving useful shelf-life of the reaction mixture.

In performing the process, 500 g of MnO₂ is placed in an oven set to400° C. for 2 hours and then heated at 110° C. for 24 hours. This MnO₂sample is mixed with Mg powder and milled following the proceduredisclosed in Example 1. The remaining steps of the process correspond tothose disclosed in Example 1, containing Mg+MnO₂.

Example 5

The following example demonstrates the method for removing residualmoisture (3.3% H₂O) from electrolytic MnO₂ to near zero level inpreparing a reaction mixture comprising Mg and MnO₂ (water-free), PlusMgCl₂ activator for improving useful shelf-life of the reaction mixture.

In performing the process, 500 g of MnO₂ is placed in an oven set to400° C. for 2 hours and then heated at 110° C. for 24 hours. This MnO₂sample is then mixed with Mg powder and milled following the procedurein Example 1. The remaining steps of the process are the same as thosedisclosed in Example 3, containing Mg+MnO₂+MgCl₂.

Example 6

The following example was performed to demonstrate the procedure forpreparing a homogeneous reaction mixture that maximizes electricalcontact of all the MnO₂ with Mg in the reaction mixture.

In performing the process, 300 g of 60μ γ-MnO₂, from Tronox, LLC, wasmixed with the Mg powder and milled according to the procedure inExample 1. The remaining process steps corresponded to those disclosedin Example 1.

Example 7

The following example was performed to demonstrate the procedureemployed in preparing a reaction mixture comprising Mg+MgCl₂ with smallparticle size (60μ) MnO₂.

In performing the process, 300 g of 60μ γ-MnO₂, from Tronox, LLC, wasmixed with Mg powder and milled following the procedure in Example 3.The remaining steps are the same as that described in Example 3.

Example 8

The following example demonstrates preparation of a reaction mixtureaccording to present invention comprising magnesium with manganesedioxide except with very small average particle size of 0.8μ.

In performing the process, 300 g of 0.8μ MnO₂ available from SigmaAldrich can be mixed with Mg powder and milled following the procedurein Example 1, above. The remaining steps of the process can follow thosedisclosed in best mode Example 1.

Example 9

The following example also demonstrates preparation of a flamelessheater reaction mixture according to the present invention, but withultra fine particulates of MnO₂ (0.8μ γ-MnO₂) hydrogen suppressant, plusMgCl₂ activator.

In preparing the reaction mixture, 300 g of 0.8μ MnO₂, from SigmaAldrich, is mixed with Mg powder and milled following the procedure ofExample 3, above. The remaining steps for preparation of the reactionmixture correspond to those also described in best mode Example 3.

Example 10

The following best mode example also demonstrates a further aspect ofthe invention except the improved flameless heater composition isprepared with two (2) times the stoichiometric amount of manganesedioxide.

In preparing the composition, 600 g of MnO₂ from Tronox, LLC, is mixedwith Mg particles and milled as described in working Example 1, supra.The remaining steps correspond to those also described in Example 1.

Example 11

The following best mode example also demonstrates a further aspect ofthe invention for preparing flameless heater compositions prepared withtwo (2) times the stoichiometric amount of manganese dioxide incombination with magnesium chloride activator.

In preparing the reaction mixture/composition, 600 g of MnO₂ fromTronox, LLC, is mixed with the Mg particles and milled in Example 1. Theremaining steps correspond to those also described in Example 3.

Example 12

The following example demonstrates a further alternative embodiment ofthe invention comprising for Mg+MnO₂+1% Zn^(o) metal, wherein anadditional alloying metal, i.e., zinc, is introduced into thecomposition to form surface alloyed magnesium metal particulates duringthe milling step.

In preparing the reaction mixture/composition, 500 g of 300μ MnO₂ (sameas the MnO₂ disclosed in Example 1, procedure for Mg+MnO₂), 69.44 g of500μ Mg (same as the Mg^(o) described in Example 1 procedure forMg+MnO₂) and 5 g Zn^(o) particles, from Sigma Aldrich with a purity of99.99%, were combined, placed in the VKE mill and milled for 6 hours.The remaining procedure is the same as that described in Example 1,procedure for Mg^(o)+MnO₂.

This inventor found that the milling process is effective for: (i)mixing the ingredients to form a homogeneous reactive composition; (ii)assures desired intimate electrical contact between the ingredients,i.e., Mg+MnO₂+Zn^(o) metal; (iii) is an effective means of formingsurfaces alloyed with added metals, such as zinc, cobalt, nickel, iron,aluminum and mixtures of the same; and, (iv) also promotes bettersurface adhesion of the MnO₂ to the magnesium or alloyed magnesium.

Example 13

This example discloses a flameless heating composition of the inventioncomprising a combination of both oxides of manganese and ruthenium in a30% RuO₂, 70% MnO₂ proportional range.

In preparing the composition, 48.61 g of 500μ Mg (same as disclosed inExample 1), 350 g of 300μ particle size of MnO₂ (same as the MnO₂disclosed in Example 1 procedure for Mg+MnO₂) and 150 g RuO₂, 99.99%pure from Sigma Aldrich (12036-10-1), were combined, placed in the VKEmill and milled for 6 hours. The remaining procedure is the same as thatdescribed in Example 1.

Example 14

This example discloses a flameless heating composition of the inventionsimilar to Example 13, except the combination of oxides of manganese andruthenium have been reversed wherein RuO₂ is present in 70% range, andthe MnO₂ is present in a proportional range of 30%.

In preparing the composition, 20.83 g of 500, Mg (same Mg disclosed inExample 1 and the procedure for milling Mg+MnO₂), 150 g of 300μ of MnO₂(same MnO₂ disclosed in Example 1 and milling procedure for Mg+MnO₂ inExample 1) Mg, and 350 g RuO₂ (same as the RuO₂ described in Example 13,Mg+30% RuO₂+70% MnO₂), were combined, placed in the VKE mill and milledfor 6 hours. The remaining procedure is the same as that disclosed inExample 1.

Example 15

This best mode example demonstrates a flameless heating composition ofthe invention comprising RuO₂ as the sole hydrogen suppressing agent.

In preparing the composition, 45.50 g of 500% Mg (same as the Mgdisclosed in Example 1) and 500 g RuO₂, (same as the RuO₂ disclosed inExample 13), were combined, placed in the VKE mill and milled for 6hours. The remaining procedure is the same as that described in Example1.

Example 16

This example demonstrates a further embodiment of the invention whereinthe flameless heater mixture includes in addition to Mg and MnO₂, 10%by-weight carbon to promote the rate of reaction and the generation ofheat.

In preparing the reaction mixture/composition, 69.44 g of 500μ Mg (Sametype of Mg disclosed in Example 1), 500 g MnO₂ (same as the MnO₂disclosed in Example 1) and 50 g carbon from Cabot Corp., Boston, Mass.,available under the trademark Vulcan XC72R, Lot: GP-3860 were combinedand placed in the VKE mill and milled for 6 hours. The remainingprocedure for this composition follows the same protocols as disclosedin Example 1, above.

Example 17

A further embodiment of the invention is presented wherein 1% Na₂S isintroduced into the flameless heater composition Mg+MnO₂ composition asa hydrogen overvoltage suppressor. A metal sulfide may be incorporatedinto the composition as a fail safe in the event hydrogen isunexpectedly generated.

The flameless heater composition was prepared by mixing 69.44 g of 500%Mg (same Mg disclosed in Example 1), 500 g of MnO₂ (same MnO₂ disclosedin Example 1) and 5 g Na₂S (from Sigma Aldrich), and placing the mixturein the VKE mill and milling for 6 hours. The remaining procedurecorresponds to that described in Example 1, above.

Example 18

Another embodiment of the flameless heater compositions of the inventionincludes the introduction of a filler/flowing agent, such as 2% SiO₂ tothe magnesium/manganese dioxide.

This embodiment may be prepared by combining 69.44 g of 500% Mg (thesame Mg disclosed in Example 1) with 500 g MnO₂ (the same MnO₂ disclosedin Example 1) and 10 g of 20μ SiO₂ (from Sigma Aldrich, purity=99.5%)and placing the mixture in the VKE mill and milling for 6 hours. Theremaining procedure for preparing corresponds to that disclosed inExample 1.

Example 19

A similar flameless heater composition to that of Example 18 may beprepared using 2% CaCO₃ filler/flowing agent with the magnesium andmanganese dioxide.

The reaction mixture/composition may be prepared by combining 69.44 g of500% Mg (same Mg as disclosed in Example 1), 500 g MnO₂ (same MnO₂ asdisclosed in Example 1) and 10 g of 20μ CaCO₃ (from Sigma Aldrich,purity=99.0%), and placing the mixture in the VKE mill and milling for 6hours. The remaining procedure corresponds to that described in Example1.

Example 20

A 99.98% pure magnesium powder of 200-300μ particle size from SuperiorMetal Powders and containing 60 ppm Al, 50 ppm Cu, 300 ppm Fe, 700 ppmMn, 50 ppm Si, 50 ppm Zn and 80 ppm Sn was used in this test. The 70-80μγ-MnO₂, from Tronox, LLC, with a purity of 99% and contained 1.2% SO₄²⁻, 2600 ppm Na, 190 ppm Al, 310 ppm C, 35 ppm Fe and 400 ppm K. Thesetwo materials were used to make a batch sample, in a stoichiometricratio according to equation [1] above, along with 5% Asbury 4827 carbon,a synthetic graphite of <20-<30μ particle size, containing 1440 ppm Al,865 ppm Ca, 2150 ppm Fe, 300 ppm Mg, 200 ppm Na and 2900 ppm Si.

Approximately 1100 g of a mixture containing 919.2 g MnO₂, 52.2 g C and130 g Mg was weighed and placed in the Vibrokinetic Energy (VKE) Mill,from Microgrinding System, Inc., model 624 (diameter=6″ and tubelength=24″). This mill is run with 36 stainless steel rods (6 with adiameter=1″, 30 with a diameter= 7/16″) with a length of 24″ as astainless steel rod. The sample mixture is loaded into the mill via the2″ diameter feed. All screws and openings are tightened and securedprior to running the mill for 1.5 hours. At the end of 1.5 hours, thesample is left in the mill for 20 minutes to cool. The sample is removedwith a Nalgene scoop, transferred to a 1000 ml stainless steel beakerand stored in a desiccator with calcium sulfate as the dehydratingagent.

A Unilayer 270 bag material from Midwest Filtration is used to containthe milled Mg/MnO₂ mixture. First, the bag material is cut into a16.5″×11″ sheet and folded in half to make a 8.25″×11″ bag. Prior toadding the sample, one of the 8.25″ sides and the 11″ side is heatsealed to form a pocket. The task is done with a Uline, 8″, ImpulseSealer (H-163). 450 g of the milled Mg/MnO₂ mixture is placed in theUnilayer Pocket and sealed closed. This completed ration heater isplaced in a UGR-E tray, over which the 3500 g “water pouch” is placed.This assembly is placed in a card board box and then 350 ml of water isadded. The card board box is then closed and the edges sealed with atape. The temperature variation was recorded as a function of time overa 60 minute period, and is presented in FIG. 8. The results of themixture of this Example is labeled “Present Invention”, while theresults of a prior art mixture is labeled “Prior Art Example 3”.

While the invention has been described in conjunction with variousembodiments, they are illustrative only. Accordingly, many alternatives,modifications and variations will be apparent to persons skilled in theart in light of the foregoing detailed description, and it is thereforeintended to embrace all such alternatives and variations as to fallwithin the spirit and broad scope of the appended claims.

1. A hydrogen suppressing, flameless, heat generating chemicalcomposition comprising a reaction mixture having at least the followingreactants: magnesium with small trace amounts of alloying metals in therange of 0.001% to 0.1% selected from the group consisting of: iron,cobalt, nickel, zinc and aluminum water; particulate carbon; a hydrogenovervoltage suppressor; a flowing agent; a reaction activator selectedfrom the group consisting of: an inorganic salt, a thermally andelectrically conducting, high surface area synthetic graphite, aconducting carbon, a conducting graphite and combinations thereof; and,a hydrogen suppressor selected from the group consisting of: γ-MnO₂,oxides of ruthenium, PtO, IrO₇, RhO₇, Fe₂O₃, Co₃O₄, NiO, Ag₂O, Au₇O₃,TiO₂, ZrO₂, HfO₂, Ta₂O₅, PbO₂, and combinations thereof, and each ofsaid reactants being present in a proportional amount to generatesufficient heat to heat water, medical supplies and/or consumablerations, wherein said chemical composition is placed in a reactionmixture bag made to be hydrophilic by dipping said reaction mixture bagin an aqueous solution containing a surfactant or by applying a dab ofsaid aqueous solution containing said surfactant on a side of saidreaction mixture bag.
 2. The hydrogen suppressing, flameless, heatgenerating chemical composition according to claim 1, wherein thehydrogen suppressor is γ-MnO₂ present in an amount ranging from 0.5 to10 times the stoichiometric amount required for the magnesium and theγ-MnO₂ reaction with water to occur.
 3. The hydrogen suppressing,flameless, heat generating chemical composition according to claim 1,wherein the hydrogen overvoltage suppressor is a metal sulfide.
 4. Thehydrogen suppressing, flameless, heat generating composition accordingto claim 1, wherein the reaction activator is magnesium chloride presentin an amount from 0.001 to 50 percent by-weight.
 5. The hydrogensuppressing, flameless, heat generating composition according to claim4, wherein the reaction activator is mixed with the reaction mixtureprior to incorporating water into the reaction mixture.
 6. The hydrogensuppressing, flameless, heat generating composition according to claim1, wherein the reaction activator is present in an amount from 0.001 to50 percent by-weight.
 7. The hydrogen suppressing, flameless, heatgenerating composition according to claim 1, wherein the reactionactivator is the synthetic graphite and the synthetic graphite is Asbury4827.
 8. The hydrogen suppressing, flameless, heat generatingcomposition according to claim 1, wherein the reaction activator is theconducting carbon and the conducting carbon is Ketjenblack, BlackPearls® 2000, Black Pearls® 1300 or Asbury TC
 307. 9. The hydrogensuppressing, flameless, heat generating composition according to claim1, wherein the reaction activator is mixed with the reaction mixture ina vibratory or ball mill for at least an hour prior to activating thereaction mixture with water.
 10. A heater device comprising the hydrogensuppressing, flameless, heat generating chemical composition accordingto claim
 1. 11. The heater device of claim 10 wherein the hydrogensuppressing, flameless, heat generating chemical composition is enclosedwithin the reaction mixture bag, the reaction mixture bag comprising afilter cloth, wherein said filter cloth comprises a 6-ply sonic bondedpolypropylene laminate.
 12. The heater device of claim 10 wherein thehydrogen suppressing, flameless, heat generating chemical composition isenclosed within the reaction mixture bag, the reaction mixture bagcomprising a dual layer bag comprising a first layer comprisingpolyester fibers and a second layer comprising polypropylene fibers. 13.The heater device of claim 10 wherein the hydrogen suppressing,flameless, heat generating chemical composition is enclosed within thereaction mixture bag, the reaction mixture bag comprising a multi-layerbag comprising a plurality of layers of polyester fibers.
 14. The heaterdevice of claim 10 wherein the hydrogen suppressing, flameless, heatgenerating chemical composition is enclosed within the reaction mixturebag, the reaction mixture bag comprising a dual layer bag comprising anouter layer of 3-ply bonded polypropylene fiber cloth and an inner layerof spunbond/meltblown/spunbond filter media comprising polypropylene.15. A meal, ready-to-eat package comprising the flameless heater deviceaccording to claim 10.